1. Field of the Invention
The present invention relates to weighing systems, and more particularly, to a system for detecting the weight of a person seated in a vehicle seat in order to determine whether to disable an inflatable safety air bag.
2. Description of the Related Art
Air bags are an important safety device included in modern motor vehicles. However, there have been injuries associated with the actuation of air bags located in front of the front passenger seat of vehicles. The occupant of the front passenger seat may be injured by the air bag if the occupant is a baby or child in a child seat, a small child, a very large adult, or a child or adult seated too close to the air bag on the front portion of the seat. Previous attempts to prevent actuation of air bags under unfavorable circumstances are known in the art. For example, U.S. Pat. No. 5,454,591 of Mazur et al., discloses a system that is intended to prevent actuation of the front passenger seat air bag if a rear-facing child seat is sensed in the front passenger seat. That system disables actuation of the air bag when, in combination, a weight sensor senses an object on the seat weighing less than a predetermined amount, a distance sensor senses a distance to an object on the seat less than a predetermined distance, and a seat belt payout sensor senses a payout greater than a predetermined amount. U.S. Pat. No. 5,474,327 of Schousek also discloses a system that is intended to prevent actuation of the front passenger seat air bag if a rear-facing child seat is sensed in that seat. That system disables actuation of the air bag when eight variable resistance pressure sensors located on a seat cushion sense an occupant weight that is less than a minimum weight, and a weight center that is forward of a reference line.
In some cases air bags can have two different deployment stages, a first stage and a second stage. Activation of the first stage, which is larger than the second stage, is dependent upon the sensed weight of the passenger.
Incorrect air bag actuation decisions by prior devices have often been the result of inaccuracies in determining the weight of the passenger, and inaccuracies in determining the location of the passenger on the seat. Variable resistance pressure sensors and other types of sensors previously utilized to determine the weight and location of a passenger suffer from inherent imprecision. Also, using pressure sensors located in, or abutting, the seat cushion also limits the accuracy of the system.